Human parvovirus B19 is a linear single-stranded DNA virus classified into Parvoviridae Parvovirus. The virus particle has an icosahedral structure, in which the capsid proteins VP1 (83 kDa) and VP2 (58 kDa) at a ratio of 1:9 constitute a capsid. The virus has no envelope. As diseases and symptoms caused by infection with parvovirus B19, erythema infectiosum (slapped cheek disease), arthritis, fetal hydrops, abortion, and the like are known.
Since one attack of human parvovirus B19 gives a person lifelong immunity, a new infection cannot be evaluated by measurement of the IgG type antibody. Accordingly, it is common to measure the IgM type antibody in order to evaluate a new infection with human parvovirus B19.
Examples of the known method of immunologically measuring human parvovirus B19 in a sample include not only an immunoassay method for an IgM type anti-human parvovirus B19 antibody, but also an immunoassay method using an anti-parvovirus B19 antibody subsequent to pretreating a sample under the condition of pH 4.0 or less (Patent Document 1), and an immunoassay method using an anti-parvovirus B19 antibody subsequent to pretreating a sample with guanidine at pH 4.5 to 6.5 (Patent Document 2). In these methods, antibodies contained in a sample are inactivated.
Also known is a method of detecting parvovirus B19 at high sensitivity by combined use of the results from an immunoassay of a parvovirus B19 antigen and the results from an immunoassay of an IgM antibody against parvovirus B19 (Patent Document 3).
On the other hand, a method of simultaneously detecting a human hepatitis C virus (HCV) antigen and an IgG type anti-HCV antibody in a sample (Patent Document 4), and a method of simultaneously detecting a human immunodeficiency virus (HIV) antigen and an IgG type anti-HIV antibody (Patent Document 5) are known.